Lecture Notes: Enteric Nervous System and Peritoneum

Enteric Nervous System (ENS)

• Branch of Peripheral Nervous System (PNS):

  • Termed as the "brain of the gut."
  • Contains about 100 million neurons from the esophagus to the gut.
  • Functions independently of the central nervous system (CNS).

• Components of ENS:

  • Myenteric Plexus:
    • Located between longitudinal and circular smooth muscle layers.
    • Controls gastric motility.
  • Submucosal Plexus:
    • Located in the submucosa.
    • Controls secretory cells.

• Types of Neurons in ENS:

  • Motor Neurons
  • Interneurons
  • Sensory Neurons: Includes chemoreceptors and stretch receptors.
    • Chemoreceptors detect pH changes.
    • Stretch receptors detect the presence of food.

• Interactions with Nervous Systems:

  • Vagus nerve (Cranial Nerve X) provides parasympathetic fibers to ENS.
  • Sympathetic nervous system inhibits ENS activity.

• Gastrointestinal Reflex Pathways:

  • Regulate secretions and motility in response to stimuli in the lumen.

Peritoneum

• Largest Serous Membrane:

  • Consists of visceral and parietal layers.
  • Visceral Layer: Known as the serosa.
  • Peritoneal Cavity: Space between visceral and parietal layers filled with serous fluid.
  • Some organs are retroperitoneal (located behind the peritoneum).

• Extensions of the Peritoneum:

  • Mesentery
  • Mesocolon
  • Falciform Ligament
  • Lesser and Greater Omentum

• Importance of Greater Omentum:

  • Acts like a "fat apron," protecting the abdominal cavity.
  • Hangs from the transverse colon to the urinary bladder.

• Conditions:

  • Peritonitis:

    • Inflammation caused by leakage from the GI tract into the peritoneal cavity.
    • Can result from trauma, rupture, diverticulitis, appendicitis, or perforated ulcers.
    • Life-threatening condition.

  • Ascites:

    • Buildup of fluid in the peritoneal cavity.
    • Causes include portal hypertension, congestive heart failure, and pancreatitis.
    • Treated with diet changes, diuretics, and paracentesis.

  • Kwashiorkor:

    • Protein deficiency leading to ascites-like symptoms.
    • Results in "swollen belly" due to osmotic imbalance and reduced albumin.
    • Common in children after weaning from breast milk to a low-protein diet.

Lecture Goals

• Describe the enteric nervous system.
• Understand the functions and locations of enteric plexuses.
• Differentiate between visceral and parietal peritoneum.
• List parts of the visceral peritoneum.
• Describe ascites and causes of kwashiorkor.